1. Technical Field
The technical field relates generally to loudspeaker arrays and array support arrangements, particularly loudspeaker arrays for an omni-directional public address and warning system.
2. Description of the Art
The art has long recognized the difficulty in obtaining substantially uniform sound propagation from an electronic warning system in all directions in a plane. Warning systems have commonly been based on multi-speaker systems utilizing rectangular speakers arranged in a circumferentially spaced relationship in a common horizontal plane. Iacono et al., in U.S. Pat. No. 4,633,229, attributed the problem on uneven distribution of sound from such a system to interference between adjacent speakers resulting in cancellation effects in certain directions. Iacono proposed a system in which adjacent loudspeakers were driven at different frequencies. While such a system should be effective in eliminating cancellation it is less useful where the intent is to broadcast intelligible speech since, among other things, there would be a change in the pitch depending on the direction from the array. The consequences for music would be stronger given there would be fewer dead moments to resynchronize signals between speakers to correct for cumulative loss of synchronization stemming the frequency differences. The directivity characteristics of sound fields for a loudspeaker system over a broad range of operating frequencies have consequences for audience coverage while retaining intelligibility for public address and other applications.